54 INHERITANCE IN SILKWORMS^ I 



from a single cocoon directly descended from the 1902 mating of 

 doubles, no doubles were obtained. 



From a large lot of eggs obtained by allowing three males from 

 doubles to mate miscellaneously with three females from singles, one 

 double and 31 single cocoons were obtained, (This lot was greatly 

 cut down by disease.) 



In no cases was a mixed double (i. e., yellow and white) produced. 



No matings on a basis of double cocooning condition were made 

 in 1904, but in the 1905 general rearings several double cocoons ap- 

 peared and from the moths obtained from them 16 matings were 

 made as follows: 11 of double with double (in one case the parents 

 were from the same triple cocoon and in two other cases from the same 

 double) ; and 5 of double with single. The proportion of doubles to 

 singles produced in 1906 from the 11 1905 matings of double with 

 double was one double to 16 singles, or a little more than 6 per cent. 

 From the mating of the two moths obtained from the same triple 

 cocoon only single cocoons were obtained. From the two matings in 

 each of which both parents were obtained from the same double cocoon, 

 in one case 12 double and 109 single cocoons were got, and in the other 

 no doubles and 57 singles. 



In 1907 a few more rearings were made from the eggs produced 

 by the mating in 1906 of moths from double cocoons. In certain of 

 these cases the parents were the offspring of moths which had issued 

 in 1905 from double cocoons. Five of these 1907 rearings represented 

 a second generation of individuals selected on a basis of double cocoon- 

 ing. In three of the cases of these five rearings each pair of parents 

 issued from the same double. And in one of these three cases the 

 grandparents had issued from the same triple cocoon. The results of 

 these three rearings were as follows : 



From two parent moths from a same double and grandparents 

 from the same triple, two double cocoons and 68 singles were obtained. 



From a second pair of parents, both from the same double, the 

 grandparents each from a double, one double and 48 single cocoons 

 were obtained. 



From another pair of parents both from the same double and 

 grandparents each from a double, 3 doubles and 73 singles were 

 obtained. 



In all the rearings (1904-5-6-7) the larvae were crowded at 

 spinning time if there were many larvae in the lot. 



The results seem to be plainly that (a) double cocooning is not 



